1. Field of the Invention
The present invention relates to an elongated vibrator made in several detachable elements assembled with each other through secured connections.
It more particularly applies to elongated vibrators notably used in methods for improving soils such as vibro-compaction, (vibro-floatation) or vibro-substitution for possibly making ballasted columns.
2. Description of the Prior Art
Generally, it is known that the elongated vibrators currently used today, consist of a tubular element which may comprise one or more sections, the upper end of which is provided with means for suspension from a hoisting and/or guiding machine and the lower end of which is connected to an endpiece successively including a damper-isolator of vibrations, a generator of vibrations and a tip provided with a protective shell.
The generator of vibrations comprises one or more eccentric flyweights rotatably mounted around the longitudinal central axis of the elongated vibrator and driven into rotation by a hydraulic or electric motor, via a coupling, or even a train of gears at a speed of rotation of the order of 1,500-3,500 rpm. The centrifugal force generated by these flyweights is exerted omnidirectionally in a plane perpendicular to the longitudinal median axis of the elongated vibrator. The order of magnitude of the centrifugal force is typically from 100 to 500 kN depending on the models.
Many technical constraints are applied to the elongated vibrator:                the centrifugal force generates strong mechanical stresses in the constitutive parts,        the thereby generated vibration creates problems of fatigue of the materials, as well as an increased risk of loosening of the screwed assemblies,        the elongated vibrator is subject to friction of the ground: all the external surfaces undergo very strong abrasion,        constraints on weight and bulkiness are added thereto,        disassembling and reassembling should be easy in order to limit stopping times on site in the case of breakdown and to limit operating costs.        
All these constraints make the design delicate. Reliability of the equipment is often uncertain.
Assemblies of the screw type are not very reliable because of the increased risk of unscrewing and of abrasion of the ground which may be exerted on the screw head, the nut or the thread itself.
The assembly type the most currently used is welding but this makes disassembly difficult, or even impossible.
Now, because of the high stresses which it undergoes, the generator of vibrations has to be able to be disassembled in order to ensure its maintenance.